Cloaking device

A cloaking device or invisibility cloak has long been featured in science fiction. Attempts have been made to devise a way to do it with objects, but results were disappointing until now. A paper in Nature Communications for September 2013 announces a new approach.^[1]

"Invisibility cloaking was almost inconceivable until the ingenious theory of macroscopic invisibility cloaking was proposed based on transformation optics principles.^[2][3] ... We successfully demonstrate the cloaking of living creatures, a cat and a fish, from the eye.^[1]

From reference 1, the two "supplementary movies" show the successful cloaking of a goldfish and a cat so far as they are within the experimental space.

Overview

A recent review said these methods were possible: ^[4][5]

1. Optical camouflage: A modified background image is projected onto a cloak of reflective material (the kind used to make projector screens). The wearer becomes invisible to anyone standing at the projection source.
2. The "mirage effect": Electric current is passed through submerged carbon nanotubes to create very high local temperatures. This causes light to bounce off them, hiding objects behind.
3. Adaptive heat cloaking: A camera records background temperatures, these are displayed by sheets of hexagonal pixels which change temperature very quickly, camouflaging even moving vehicles from heat-sensitive cameras.
4. Calcite crystal prism: Calcite crystals send the two polarizations of light in different directions. By fixing prism-shaped crystals together in a particular way, polarised light can be directed around small objects. This effectively cloaks them.